Can You Have Too Much Oxygen in a Fish Tank?

Last Updated on August 6, 2020

Fish need oxygen to live just like us humans. We inhale air that has oxygen and exhale air that has carbon dioxide. That is a basic need to sustain life. But can you have too much oxygen in a fish tank?

Fish get their oxygen from the dissolved oxygen in the water. They absorb this oxygen and release carbon dioxide through their gills.

Providing adequate amounts of oxygen in our fish tanks is very important. It is highly unlikely that you will have too much oxygen in your fish tank unless you are pumping in pressurized oxygen into the fish tank. Let us discuss this and give the best environment to our Betta fish.

How do I oxygenate my fish tank?

The large bodies of water such as oceans, rivers, lakes, and streams have constant water turnover and the currents are constantly moving the water along. The air from the atmosphere also exerts its influence on these bodies of water forming ripples and waves.

This continuous movement of air and water allows gas exchange to occur. Oxygen from the air enters while carbon dioxide exits from the water. This gas exchange is very important for aquatic life to thrive.

The water of your fish tank is in constant contact with the air and this meeting point is where oxygen enters the water column. But you need to agitate the water to simulate the water currents and flow to allow gas exchange to occur.

Agitation of the water surface therefore is important to ensure that oxygen enters your fish tank for your fish to breathe. Here are a few ideas to get oxygen flowing into your fish tank.

1. Get a bigger tank

It is good to remember that a larger volume fish tank with a wider surface exposed to air is easier to aerate than a small tank. This is one reason why it is better to put a Betta fish in a 5 gallon tank instead of a 1 gallon bowl.

2. Use a filter that has a feature to create water agitation

A sponge filter is air driven and the air bubbles that rise to the surface create a flow from the bottom and stirs the water. The bubbles break the surface tension of the water allowing gas exchange to occur. This filter is great for a Betta fish because it doesn’t create too strong currents that can blow away your Betta fish. 

A hang on a back filter with a trickle feature will also be a good choice. Just keep the outflow at a low setting so you do not stress out your Betta fish with a very strong current.

3. Consider keeping live plants

Live aquatic plants will release oxygen as a by-product of photosynthesis when they are exposed to light. Be careful though because they consume oxygen when it is dark and this will lower the oxygen levels in your fish tank if you do not have enough surface agitation. A betta fish will gulp air from the surface so just keep the surface accessible by not filling it up too much with floating plants.

Related: Can Fish Sleep with the Air Pump On?

Can You Have Too Much Oxygen in a Fish Tank

How much is too much oxygen for fish?

The recommended oxygen level for a freshwater fish tank is at 8.3 PPM (a range from 7 to 10 PPM is normal) and you can measure this by using dissolved oxygen meters. This is a rather expensive device and an alternative would be to use an oxygen chemical test kit. Another excellent way of knowing whether there is enough oxygen is by observing your fish.

Too much oxygen in a fish tank at 150% saturation may trigger lethal gas bubble disease in which bubbles will form within the blood of the fish creating bubbles in its skin and eyes. Gas bubbles can even form in the fish’s internal organs and lead to death. This is rare for an aquarium setup unless you are pumping in pressurized oxygen into your fish tank which is highly unlikely.

Too little oxygen starting at 4 PPM will cause your fish to gasp for breath as though they are panting. You can observe excessive gill movement can and staying near the water surface gasping for air. Low levels of oxygen is hypoxia. Long-term lack of oxygen will lead to acidosis meaning acidity of their blood increases and this will kill your fish. If oxygen goes below 2 PPM, then fish will soon die.

Can fish live without air pump?

Larger fish might not last long without an air pump because their oxygen demands are higher than smaller fish.

A betta fish can live without an air pump because it has a labyrinth organ that allows it to absorb oxygen from the air it gulps from the surface of the water. Betta fish have developed in such a way that it can survive water with lower oxygen levels.

They can also use their gills for getting oxygen too which gives them quite an advantage in survival. This however should not be an excuse for you not to provide a healthy home for your Betta fish.

Related: Do Bettas Need Air Pump?

Are air bubbles good for fish tank?

Bubbles from an air stone is fine as long as it doesn’t create a very harsh flow that stresses out your Betta fish.

It is also normal to see water bubbles on the glass after doing water changes. These will disappear after a few hours.

Dead algae, plants, and other rotting material may form small bubbles as decomposition takes place. This isn’t oxygen and the decay must be out of the tank to reduce the chance of having ammonia spikes.

Male betta fish will make bubble nests on the water surface and this may be a sign that you have a happy and healthy male betta fish ready to breed.

Too much oxygen in a fish tank is highly unlikely unless you are introducing pressurized oxygen into the water column. Regular aquarium equipment such as air pump driven sponge filters or hang on back filters help keep oxygen levels within the optimal range for your betta fish tank. Water surface agitation is the key for constant gas exchange to occur.